@Rumraket , @Faizal_Ali , @Roy , @Mercer
Ya know, you guys might actually have to read the book to understand it. Most of the evolutionary analysis here is based on bad concepts of the arguments. Is that why you’re asking us to summarize it for you?
But watch out, you might find some things in the book interesting: https://www.youtube.com/watch?v=fqiXgtDdEwM
This looks good until you realize antibodies can bind to any spot on an antigen that happens to have a sequence that can act as the complement. So the location is somewhat random and there are no further implications. For a protein complex, you need the complement at a “right” location so that the resulting quaternary structure has meaningful catalytic activity. Even if you get complementary binding sites, having an active protein complex is far from given. The requirements for protein complexes are many orders of magnitude more stringent than B cells.